linux-kernel - Re: [PATCHv5 04/15] hwspinlock/core: add common OF helpers

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Date:	Thu, 3 Jul 2014 10:15:38 +0300
From:	Ohad Ben-Cohen <ohad@...ery.com>
To:	Suman Anna <s-anna@...com>
Cc:	Mark Rutland <mark.rutland@....com>,
	Kumar Gala <galak@...eaurora.org>,
	Tony Lindgren <tony@...mide.com>,
	Josh Cartwright <joshc@...eaurora.org>,
	Bjorn Andersson <bjorn@...o.se>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	linux-arm <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCHv5 04/15] hwspinlock/core: add common OF helpers

Hi Suman,

On Thu, Jul 3, 2014 at 12:14 AM, Suman Anna <s-anna@...com> wrote:
>> Do we have a use case today that require the xlate() method?
>>
>> If not, let's remove it as we could always add it back if some new
>> hardware shows up that needs it.
>
> The xlate() method is to support the phandle + args specifier way of
> requesting hwlocks, platform implementations are free to implement their
> own xlate functions, but the above supports the simplest case of
> controller + relative lock index within controller.

Do we have a use case for a different implementation other than the
simplest case? If not, it seems to me this will just become redundant
boilerplate code (every platform will use the simple xlate method).

> This function again is to support the phandle + args specifier way of
> requesting hwlocks, the hwspin_lock_request_specific() is invoked
> internally within this function, so we are still reusing the actual
> request code other than handling the DT parsing portion. If we go back
> to using global locks in client hwlocks property, we don't need a
> of_hwspin_lock_get_id(), the same can be achieved using the existing DT
> function, of_property_read_u32_index().

I think you may have misunderstood me, sorry. I'm ok with the phandle
+ args specifier. I just think we can use it, together with the
base_id property, to infer the global lock id from the DT data. This
is not only a must to support heterogenous multi-processing systems,
it will also substantially simplify the code.

Thanks,
Ohad.
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